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A new three-year $660,000 grant from the US Department of Energy (DOE) will fund researchers at the Georgia Institute of Technology (Atlanta) on development of advanced additive manufacturing techniques used to create 3D nanoscale structures.

The research will use a technique employing high-speed, thermally energized jets in delivering precursor materials and inert gas that dramatically accelerates growth while improving the purity and increasing the aspect ratio of the 3D structures. Known as focused electron beam induced deposition (FEBID), this technique delivers a tightly-focused beam of high-energy electrons and an energetic jet of thermally excited precursor gases, both confined to the same spot on a substrate.

Secondary electrons generated when the electron beam strikes the substrate cause decomposition of the precursor molecules, forming nanoscale 3D structures whose size, shape and location can be precisely controlled, according to the researchers. The gas-jet-assisted FEBID technique allows fabrication of high-purity nanoscale structures using a wide range of materials and combination of materials.

“This unique nanofabrication approach opens up new opportunities for on-demand growth of structures with high aspect ratios made from high-purity materials,” said Andrei Fedorov, a professor in Georgia Tech’s Woodruff School of Mechanical Engineering and the project’s leader. “By providing truly nanoscale control of geometries, it will impact a broad range of applications in nanoelectronics and biosensing.”

The researchers have demonstrated the feasibility of the technique, and expect the grant to help them develop an understanding of how the process works, accelerate the rate of materials growth and provide improved control over the process. The research will include both theoretical modeling and experimental evaluation. Proof of principle for using the jets as part of the FEBID technique was reported by Fedorov’s group in the journal Applied Physics Letters in 2011.

By allowing the rapid atom-by-atom “direct writing” of materials with controlled shape and topology, the work could lead to a nanoscale version of the 3D printing processes now revolutionizing fabrication of structures at the macro scale. The technique also could be used to produce nano-electromechanical sensors and actuators, to modify the morphology and composition of nanostructured optical and magnetic materials to yield unique properties, and to engineer high-performance interconnect interfaces for graphene and carbon nanotube-based electronic devices.“Wherever electrons strike the surface, you can grow the deposit,” explained Fedorov. “That provides a tool for growing complex three-dimensional structures from a variety of materials with resolution at the tens of nanometers. Electron beam induced deposition is much like inkjet printing, except that it uses electrons and precursor molecules in a vacuum chamber.”

Major challenges lie ahead for using the technique to manufacture 3D nanostructures including increasing the rate of deposition and eliminating the unwanted deposits of carbon that are formed as part of the process. Fedorov and his team are using energetic jets of inert argon gas to clean substrate surfaces and carefully tune the energy of the desired molecules delivered in another jet to enhance the rate at which the precursor sticks to the substrate.

“If the energy of the jet is sufficiently high, the inert gas molecules striking the surface can knock away the adsorbed hydrocarbon contamination so that there is no parasitic carbon co-deposition,” he said. “We can also tune the properties of the precursor molecules so they stick more effectively to the surface. We have shown that we can increase the rate of growth by an order of magnitude or more while maintaining a high aspect ratio of deposited nanostructures.”

To date, about two dozen materials have been successfully deposited using FEBID on different substrates, including semiconductors, dielectrics, metals and even plastics. The researchers aim to create nanostructures containing more than one material, allowing them to create unique properties not available in each individual material.

Some examples could include new types of ferromagnetic materials and photonic bandgap structures with unique properties. Fedorov’s group has used FEBID to fabricate low-resistance contacts to carbon nanotubes and graphene, a unique carbon-based material with attractive electronic properties. For more information, see www.georgiatech.edu. ME

Industry, Technology Updates from SME Technical Communities

Member leaders from SME’s technical communities presented industry outlooks at the SME Annual Conference in June. Several technical papers update developments in forming and fabricating (TP13PUB59); plastics, composites and coatings (TP13PUB61); product and process design and management (TP13PUB62); rapid and additive manufacturing (TP13PUB63); and manufacturing education and research (TP13PUB60).

The forming and fabricating forecast is hopeful, with expansion expected in transportation and energy markets as well as a continued revolution in new—often nonmetal—materials and innovative joining technologies in traditional segments of manufacturing, such as aerospace and automotive. Among the innovations in plastics, composites and coatings are forged composites, particularly for automotive applications, thermal insulating ceramic coating, dry film lubricant, rapid-cure carbon thermoset composite materials/processes and nanomaterials to influence material properties. Software advances for injection molding and mold design are improving simulation and flow analysis.

On the product and process design and management front, important topics continue to be change management—emphasizing the triple bottom line of profit, people and planet, knowledge management—with an increasing need to manage and leverage intellectual property, and shop floor information delivery and mobile devices, so employees have the data they need when and where they need it.

A unified approach—within SME and in collaboration with other organizations, government agencies and educational institutions—in support of manufacturing education is outlined in the update from SME’s Manufacturing Education & Research community. Ongoing efforts emphasize the importance of manufacturing and well-educated workforce to a robust economy. The central role of the “Four Pillars of Manufacturing Knowledge” model is described as well.

Several other new tech papers are from the SME Annual Conference breakouts sessions on “Innovations That Could Change the Way You Manufacture.” Authors from General Motors Global R&D (www.gm.com/design-technology; Warren, MI) describe a multi-ring domed electrode for aluminum resistance spot welding (TP13PUB55). The greatest benefit of this technology is the large resistance spot welding process window that it displays for welding of aluminum sheet, extrusion, casting or combinations thereof, while also achieving high weld quality and eliminating surface expulsion. 3D printing of silicon micro and nano structures by ion implantation, silicon deposition and selective silicon etching (TP13PUB58) is described by authors from KTH Royal Institute of Technology (www.kth.se; Stockholm, Sweden). The proposed technology could change and greatly simplify the fabrication of many MEMS, NEMS and silicon photonic devices without requiring a fully equipped semiconductor cleanroom. ME